1. Field of the Invention
This invention relates to an apparatus for indicating a direction for adjusting the height of the apparatus to an appropriate height (hereinafter the direction is referred to as "the direction of an appropriate height) so as to enable an operator to recognize it visually and dynamically.
2. Description of the Prior Art
In construction of the land readjustment of housing sites or agricultural fields, it is performed to level the ground. For the construction, large-sized construction machines, such as a bulldozer and a crawler, are used, and the ground is dug and moved by means of the blades of the machines so as to achieve a finished surface which conforms to a site plan. In this ground-leveling operation, surveys are made before and during the operation. Places, on which the ground should be banked or from which the ground should be removed, are determined by the survey made before the operation, and the ground-leveling operation is repeatedly performed in accordance with measured values obtained by the survey, which is carried out as occasion demands, during the operation. As a result, the ground is leveled to conform to the site plan.
An example of such a surveying operation is as follows.
First, a surveyor vertically sets a pole at a place to be surveyed. After that, another skilled surveyor collimates the pole with an optical level and reads numerical values indicating the height at the level. This operation is repeatedly performed, and thereby a plurality of places to be surveyed are measured to calculate differences in elevation among the places.
In recent years, however, a surveying operation in which a rotational laser apparatus cooperates with an appropriate-height displaying apparatus has been employed from the viewpoint of the speedup of construction, the reduction of man-hours, and the reduction of labor costs.
The rotational laser apparatus emits a laser beam in a horizontal direction while rotating so as to form a reference plane of the laser beam. The appropriate-height displaying apparatus receives the emitted laser beam, and then displays the direction of a deviation of an appropriate height from the height of the reference plane of the laser beam.
An example of the aforementioned case is shown in FIG. 1. Reference numeral 1 denotes a rotational laser apparatus, and 2 denotes an appropriate-height displaying apparatus. The rotational laser apparatus 1 is fixed on a tripod 3 which is set at a predetermined place K. A reference plane is formed by a laser beam P projected from the rotational laser apparatus 1. The appropriate-height displaying apparatus 2 is fixed on, for example, an attachment pole 6 which is stood on a blade 5 of a bulldozer 4. Thereby, the height from the ground surface of the predetermined place K to the reference plane of the rotational laser apparatus 1 is correlated with the height from the appropriate-height displaying apparatus 2 to an edge 5a of the blade 5. Accordingly, if the construction is carried out such that the appropriate-height displaying apparatus 2 receives a projected laser beam at a position of a predetermined height, the ground leveling operation can be performed at a predetermined ground level.
As shown in FIGS. 2 and 3, the appropriate-height displaying apparatus 2 generally comprises a displaying apparatus body 7, a plurality of light sources 8 for display, a pair of light receiving portions 9, and a control portion disposed inside of the displaying apparatus body 7. In the light sources 8, each three of them makes a set, and sets in the upper, middle, and lower parts of the apparatus body 7 serve as display portions 8a, 8b, 8c, respectively. Electric power to the appropriate-height displaying apparatus 2 is supplied from a battery of the bulldozer 4. Reference numeral 10 denotes a connector for the power source.
In this conventional appropriate-height displaying apparatus 2, the three light sources 8 of the display portion 8a are simultaneously turned on when the appropriate height of the apparatus 2 is greater than its actual height at that moment. On the other hand, the three light sources 8 of the display portion 8c are simultaneously turned on when the appropriate height is lower than the actual height at that moment. The three light sources 8 of the display portion 8b are simultaneously turned on when the appropriate height is equal to the actual height at that moment.
By the conventional appropriate-height displaying apparatus, it is needed to recognize the position of a display portion which is in an ON-state in comparison with the position of display portions which are in an OFF-state in order to determine which of the display portions 8a, 8b, 8c is lighting. Therefore, by the conventional apparatus, disadvantageously, it is impossible to intuitively recognize information on the direction of the appropriate height in comparison with the actual height at that moment.
This disadvantage is not overcome by conspicuously flashing the display of the light sources 8. Nor is the disadvantage overcome by increasing the brightness of light emitted by the light sources 8. As a solution to this, it can be expected to display information on the direction of the appropriate height by the use of signs, such as arrows, or words, such as "up" and "down".
However, these display methods do not enable intuitive recognition of the information on the direction of the appropriate height in comparison with the actual height at that moment because, according to the display methods, the whole of figures or words must be visually recognized in order to judge the direction to adjust the height of the displaying apparatus to the appropriate height. In addition, if the display, which is in a static state and is inconspicuous, is attempted to be made conspicuous, power consumption is enlarged, and thereby another power source provided in a machine body or the like would be required.